Question : The angle of depression of a point situated at a distance of 70 m from the base of a tower is $60^{\circ}$. The height of the tower is:

Question : A pilot in an aeroplane at an altitude of 200 metres observes two points lying on either side of a river. If the angles of depression of the two points be $45^{\circ}$ and $60^{\circ}$, then the width of the river is:

Question : The tower is 50 metres high, its shadow is $x$ metres shorter when the sun's elevation is $45°$ than when it is $30°$. The value of $x$ (in metres) is:

Question : If the angle of elevation of the sun changes from 45° and 65°, then the length of the shadow of a pillar decreases by 10 m. The height of the pillar is:

Question : Let ABC be a right-angled triangle where $\angle \mathrm{A}=90^{\circ}$ and $\angle \mathrm{C}=45^{\circ}$. Find the value of $\sec \mathrm{C}+\sin \mathrm{C} \sec \mathrm{C}$.